The present invention relates to an improved bellows sealed 1/4 turn valve in which the linear movement of a valve actuator shaft is converted to rotational movement of the 1/4 turn between the valve and the bellows seal to provide enhanced valve integrity.
A 1/4 turn valve, sometimes referred to as a ball valve when the plug is so shaped, comprises a valve body with an inlet passage, an outlet passage and a valve chamber between the inlet and outlet passages. The valve chamber generally has the shape of a body of revolution such as a sphere, a cylinder, or the frustum of a cone, with its axis of rotation usually perpendicular to the inlet and outlet passages which are usually colinear. A valve plug shaped generally to conform to the shape of the valve chamber is rotatably disposed within the chamber. The valve plug is generally a solid body with a flow passage therethrough. The flow passage is positioned such that when the valve plug is in an open position the flow passage is aligned to provide fluid communication between the inlet and outlet passages. When the valve plug is rotated to a closed position usually at a position 90.degree. from the open position, a 1/4 turn, the flow passage is not aligned with the inlet and outlet passages, and solid portions of the valve plug interrupt fluid communication therebetween. A complete practical 1/4 turn valve also includes connecting means such as threads or flanges at the openings of the inlet and outlet passages so that the valve may be connected into a fluid pipeline or a conduit to provide control of fluid flow therein. A 1/4 turn valve also includes rotating means so that the valve plug may be rotated between the open and closed positions. The rotating means usually is a valve stem extending through the valve body and sealed with packing in a manner well known in the art. Most 1/4 turn valves, mainly ball valves, have elastomeric seals to enhance the sealing properties, so that leakage from passageways cannot communicate through the valve cavity. Previously, the valve stem was rotated manually, or was controlled, but in hazardous environments valve actuation is usually remotely controlled.
1/4 turn valves of the type described are often used in chemical processing applications such as in nuclear fuel processing plants. In such plants, 1/4 turn valves are used for cell wall block valves or they may be used in pipelines containing nitric acid, hydrofluoric acid, sulfuric acid or sodium-hydroxide, or where there is present hydrogen sulfide contaminated petroleum and radiactively contaminated fluids, biologically sterile fluids, and where vacuum leakage is critical. Often in such plants the materials which are controlled by the 1/4 turn valves are toxic so that the sealing requirements for such valves are of a higher degree than in the normal commercial situation. In such a case, it is common for bellows sealed 1/4 turn valves to be used because the bellows sealed 1/4 turn valves are hermetically seal welded as the primary seal in the valve. Some advantages of 1/4 turn valves are low maintenance, high reliability, and the ability for a full-ported flow passage, resulting in minimum fluid pressure drop across the valve. Secondary seals are of the traditional sort including elastomeric gaskets and the like. Heretofore, 1/4 turn valves when used with bellows seals have not had mechanisms available to change linear motion to rotational motion between the valve body and the bellows. The use of hermetic bellows sealed values is important because it permits the contaminated materials to be sealed by metal bellows which are more likely to retain their integrity for a longer life span, an important feature when hundreds of such valves are used in a single plant, a when the contaminated nature of the environment is considered with the attendant problems of changing or repairing faulty valves.
Accordingly, it is an object of the present invention to provide a bellows sealed 1/4 turn valve wherein means are provided for translating linear motion to rotational motion between the bellows seal and the valve body.